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Historic Preservation - Technical Procedures

Spectitle:
Concealing Water Stains On Plaster Surfaces

Procedure code:
0920014R

Source:
Internet - Zinsser Products

Division:
Finishes

Section:
Lath & Plaster

Last Modified:
02/24/2012

Details:
Concealing Water Stains On Plaster Surfaces



CONCEALING WATER STAINS ON PLASTER SURFACES


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on concealing water
         stains on plaster walls or ceilings using a shellac-based
         primer sealer. A product, such as white-pigmented shellac
         can be used to seal, prime and block out existing stains,
         prohibiting them from bleeding through finish layers of
         paint.

    B.   See 01100-07-S for general project guidelines to be
         reviewed along with this procedure.  These guidelines
         cover the following sections:

         1.   Safety Precautions

         2.   Historic Structures Precautions

         3.   Submittals

         4.   Quality Assurance

         5.   Delivery, Storage and Handling

         6.   Project/Site Conditions

         7.   Sequencing and Scheduling

         8.   General Protection (Surface and Surrounding)

         These guidelines should be reviewed prior to performing
         this procedure and should be followed, when applicable,
         along with recommendations from the Regional Historic
         Preservation Officer (RHPO).


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   William Zinsser & Co., Inc.
         173 Belmont Drive
         Somerset, NJ 08875
         800/469-4539
         FAX 908/469-4539

    B.   Masterchem Industries, Inc.

2.01 MATERIALS

    A.   White-pigmented shellac such as "Kilz" (Masterchem
         Industries, Inc.), "Bin" (William Zinsser & Co., Inc.),
         or approved equal.  Both are available from hardware
         stores in spray cans or brushable liquid.

2.02 EQUIPMENT

    A.   Clean sponge

    B.   Stiff, fiber bristle brush

    C.   Paint brush, roller or airless sprayer


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Before proceeding with steps to conceal water stains,
         examine the plaster and substrate material for potential
         sources of moisture and make repairs as required.  For
         guidance on cleaning and/or repairing damaged plaster,
         see 09200-01-S, 09210-02-R, 09210-03-R and 09210-05-R.

         1.   Look for signs of water infiltration:  Examination
              may show where the water is entering.

         2.   If possible, examine the condition of the back-up
              material:  

              a.   CAREFULLY EXAMINE the wall for open gaps or
                   cracks in joints and around openings that
                   could allow water to enter the building.  

                   1)   Are joints properly caulked or sealed?  

                   2)   Are flashings and drips in good
                        condition?

                   3)   Are there open or eroded mortar joints in
                        copings or in sills?

              b.   Carefully note the condition and profile of
                   the mortar joints.

              c.   Repair cracks in masonry and/or repoint as
                   necessary before proceeding with the cleaning
                   operations.

         3.   Examine wall sections and details of construction:
              Carefully examine roof and wall junctures and
              flashing details for possible sources of moisture
              entry.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   After source of moisture has been eliminated, allow the
         surface to thoroughly dry out.

    B.   Carefully remove any surface deposits and loose paint
         using a stiff fiber bristle brush only.  Fill cracks and
         holes as required.

    C.   Wipe the surface with a clean, damp cloth.

    D.   Apply white-pigmented shellac over the stained area using
         a brush, roller or airless sprayer.  Follow
         manufacturer's instructions.

         1.   Depending on the severity of the stain, multiple
              coats may be required.  If so, allow the first coat
              to thoroughly dry (typically 45 minutes) before
              proceeding with additional coats.  

         2.   If using a brush or roller, apply additional coats
              in the same direction as the first coat.

         3.   If the surface is to be repainted with a high-
              hiding paint, spot-priming only the stained areas
              is acceptable.  However, if a high-hiding paint is
              NOT used to finish the surface, spot-priming is NOT
              RECOMMENDED, as primed areas may appear shiny
              through the paint finish.  (Note: Many ceiling
              paints have little hiding strength).  In such
              cases, the entire wall or ceiling surface should be
              primed with the white-pigmented shellac before
              repainting to produce a more uniform final
              appearance.

    E.   Prime and repaint the entire surface with oil or latex
         paint as required.  For guidance on painting, see 09900-
         07-S and 09900-08-S.

                         END OF SECTION